1. Field of the Invention
The invention relates to a glue for sealing the side seams of smokable articles as well as a method for the production of such a glue.
2. Description of the Prior Art
During the last few years the production of factory cigarettes has undergone great technological changes. While the principle of the rod-forming machine, the rod maker, has not been fundamentally changed, the production rate reached with the use of new machine generations very high piece numbers (10,000 cigarettes/minute) corresponding to a rod speed of 630 m/minute. The use of these high-speed machines must therefore go hand in hand with the adaptation of the basic materials for the tobacco rod production. In particular, the seam sealing process must be improved in accordance with the new requirements.
The seam glues used nowadays are based on the following chemical types:
1) Polyvinyl alcohols =non-natural origin PA0 1) Starch, dextrin =natural origin PA0 3) Gelatine =natural origin PA0 1) The attainable processing rates are at 5000 cigarettes/minute at the maximum, i.e. do not allow the use of modern cigarette machines. PA0 2) The solids concentration is about 30% at the maximum with starch/dextrin, i.e. far below that of PVA glues by about 50%; due to this, the bleeding effect can become a problem. PA0 3) Their viscosity is higher and requires other, more expensive application systems. PA0 4) Their high germ count load must be reduced by additives or physical measures (long-term stability). PA0 5) The formation of smoke-sensorily active combustion products which negatively influence the smoke product quality. PA0 6) The temperature of the seam heater necessary for evaporating the liquid portion must be higher due to the weaker wet-gluing behavior and the higher water content.
Polvinyl alcohols (PVA) comply with all requirements both in machine-technological and in smoke-sensory respect. In particular, the use of simple dosing systems (gravity feeder) and the resistance against bacteria decomposition and fungus or mold formation explain the preferred use of PVA dispersion glues in the cigarette industry. However, attempts are being made to question the approval of PVA glues for use in the tobacco industry.
At the present stage of development, starch/dextrin and gelatine have several disadvantages as compared with the PVA glue, which are an obstacle to their broader application. In this connection the following disadvantages must above all be mentioned: